This invention is related to a device for relative displacement of two elements comprising articulated links arranged between the elements and force-applying arrangements for applying force for the relative displacement of the elements.
The relative displacement of the two elements has the purpose to position them mutually in a manner aimed at by means of the force-applying arrangements. More specifically, the device according to the invention is intended to form a manipulator or robot. The second of the elements is intended to carry, directly or indirectly via a carrying arrangement, a working member to execute the function aimed at, for instance picking, placing, packing and palletising. However, it is remarked that the working member may be adapted to carry out also other work operations than those just mentioned. The first element may according to a first embodiment form a base member secured in space but could according to a second embodiment form a base member with the character of a carrier movable in relation to a carcass. A force-applying arrangement then serves for adjusting the position of the carrier in relation to the carcass.
A robot of the kind defined by way of introduction is described in U.S. Pat. No. 4,976,582. For the positioning of the second element, the robot comprises three force-applying arrangements, which in unison comprise three force-exerting members arranged in a triangular distribution on the first element. Each of the force members is connected to the movable second element via its own connection comprising two link arrangements and an intermediate connection arrangement. These three connections coupled in parallel are likewise arranged in a triangular distribution. Each of these connections comprises a first link arrangement including two first links pivotably connected to the second element and a second link, which is rigidly connected to a movable portion of the force-exerting member and which by means of a connection arrangement is connected to the two first links. The second link is movable with regard to one single degree of freedom relative to the stationary portion of the force-exerting member. The connection arrangement connects the first and second links in a hinged manner with two but not more than two degrees of freedom. The link arrangement formed by the first links is connected to the second element so that likewise two but not more than two degrees of freedom occur. In reality, the first link arrangements form parallelogram-shaped four-links systems. A disadvantage with this known type of robot is that it becomes comparatively bulky as a consequence of the triangular distribution discussed hereinabove. The angle between planes of pivoting for two adjacent second links must, namely, always be less than 180xc2x0. Thus, it is very difficult to arrange two or more of those robots closely to each other without collision. A further disadvantage is that all arms must be of equal length. This implies that it is not possible to optimise the robot to the pattern of movement in question. Performance will always be symmetrically distributed in a symmetrical working area, which is not cost efficient.
As a consequence of the equilateral triangular construction of the known robot it is also difficult to arrange to work horizontally above conveyors, loading pallets etc.
This invention aims at devising routes to develop the device of the kind defined by way of introduction so as to eliminate or at least reduce one or more of the disadvantages mentioned hereinabove. A particular aim is to provide a greater flexibility as to the design of the device so that two or more devices may be placed to work comparatively close to each other. According to a further aspect, the aim is to provide an enhanced movability of the robot.
The object of the invention is achieved in that the articulated links form at least one four-links system, that the device also comprises at least one pivot arm arrangement and that the fourlinks system and the pivot arm arrangement are mutually connected by means of a connection arrangement.
The invention creates possibilities for an asymmetrical design of the device according to the invention and accordingly a design adapted for the purpose of the working area thereof. For instance, this asymmetrical character of the device according to the invention provides possibilities for a very dense packing of a plurality of robots.
Several preferable developments of the invention are defined in the dependent claims. These developments and advantages in connection with the invention are dealt with more specifically in the following description.
With reference to the enclosed drawings a more close description of embodiment examples of the invention follows hereunder.